Hydraulic Ride Control System with Manual Mode Safeguard

ABSTRACT

A hydraulic ride control system for mobile machine having an implement is disclosed. The ride control system may include a hydraulic actuator extending from the machine and connected to an implement, an accumulator, a valve controlling fluid flow between the hydraulic actuator and the accumulator, a sensor, a ride control selection switch and, a controller receiving signals from the sensor and the ride control selection switch and when the ride control switch is in manual position, only allowing fluid flow between the hydraulic actuator and the accumulator when the sensor indicates a predetermined value.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to hydraulic systems and, more particularly, relates to hydraulic ride control systems for mobile machines.

BACKGROUND OF THE DISCLOSURE

Mobile machines used in industrial, construction and agricultural settings may often be subjected to bouncing, pitching, or loping when encountering uneven or rough terrain. Such mobile machines may include but not be limited to wheel loaders, excavators, motor graders, bulldozers, backhoes, pipe layers and the like. As such machines typically do not include shock absorbing systems, when the mobile machine traverses uneven or rough terrain, particularly when the mobile machine is carrying a load, the machine is often subjected to significant vibrations or bouncing. The substantial weight of the work implement and its associated load tends to exacerbate these moments, resulting in increased wear of the machine and discomfort for the operator.

In order to mitigate such loping or bouncing, such mobile machines are often provided with a ride control system which employs mechanisms for reducing the likelihood of that jolt being communicated back to the operator. For example, if the machine is traversing rough terrain, these resulting forces can often cause the hydraulic actuator connected to the implement to experience significant forces. But for inclusion of a ride control system, those forces can often be communicated back to the operator in terms of the ride experienced by the operator, or the actuator levers held by the operator being jerked, sagged, dropped, or otherwise moved within the hands of the operate. An accumulator is therefore often provided to either absorb the pressurized fluid exiting the hydraulic actuator upon traversing such terrain, or to direct pressurized fluid back to the actuator.

Such mobile machines are often designed to operate in many different modes. For example, such mobile machines are often able to operate in an “automatic” or “auto” mode wherein the ride control system automatically engages upon the mobile machine reaching a predetermined speed. Another mode is simply an “off” mode wherein the ride control system is simply not used regardless of speed or any other parameter. A third mode, often referred to as “manual”, or “service” mode, enables the ride control system to be serviced or in other words have maintenance performed on the system. With current mobile machines, when the manual mode is selected, the ride control system is always actuated. Given the extreme pressures which the hydraulic actuators may be required to operate under, these pressures can be communicated back through the valving of the ride control system and overpower same. This can result in significant damage to, if not entire failure of, the valving of the ride control system. For example, after performing maintenance on such a mobile machine, the ride control system may inadvertently still be left in the manual mode, and then, when placed back into operation, the valving of the ride control system can be subjected to pressures well beyond its design constraints and ultimately be damaged or fail.

Accordingly, a hydraulic ride control system which is able to provide ride control when needed and which avoids such damage is needed in the industry.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a hydraulic ride control system for mobile machine having an implement is therefore disclosed. The ride control system may include a hydraulic actuator extending from the machine and connected to an implement, an accumulator, a valve controlling fluid flow between the hydraulic actuator and the accumulator, a sensor, a ride control selection switch, and a controller receiving signals from the sensor and the ride control selection switch and, when the ride control switch is in manual position, only allowing fluid flow between the hydraulic actuator and the accumulator when the sensor indicates a predetermined value.

In accordance with another aspect of the disclosure, a method of controlling the ride of a mobile machine having an implement is disclosed wherein the method comprises detecting the position of a ride control switch, sensing a parameter indicative of movement of the mobile machine, and when the ride control switch is detected to be in a manual mode, allowing activation of ride control only when the sensed parameter indicates the mobile machine is not moving.

In accordance with another aspect of the disclosure, a mobile machine is disclosed which may comprise a chassis, an engine supported on the chassis, a traction device supporting the chassis, an implement movably connected to the chassis, a hydraulic actuator connected between the implant and the chassis, a ride control system, a ride control selection switch, a sensor sensing a parameter indicative of movement of the mobile machine, and a controller engaging the ride control system when the ride control selection switch is in a manual mode only if a sensed parameter from the sensor reaches a predetermined value.

These and other aspects and features of the disclosure may come more readily apparent upon reading the following detailed description when taken in conjunction in with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a mobile machine constructed in accordance with the teachings of the present disclosure;

FIG. 2 is a hydraulic schematic illustrating the ride control system of the present disclosure;

FIG. 3 is a schematic representation of the controller of the ride control system of the present disclosure; and

FIG. 4 is a flow chart depicting sample sequence of steps which may be practiced by the software or logic employed by the hydraulic ride control system.

While the following detailed description will be given with respect to certain illustrative embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breath and spirit of the disclosure is broader than the embodiments specifically disclosed herein and encompassed within the claims appended hereto.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to the drawings, and with specific reference to FIG. 1, a mobile machine constructed in accordance with the teachings of the disclosure is generally referred to by reference numeral 10. The machine 10 may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, the machine 10 may be an earth moving machine such as a loader, an excavator, a backhoe, a motor grader, a dump truck, or any other earth moving machine. The machine 10 may include a chassis 12, a work implement 14 movably attachable to chassis 12, an operator cabin 16 supported by the chassis for operator control of the work implement 14, a power source 18 operatively connected to drive a traction device 19, and one or more hydraulic actuators 20 connected to move the work implement 14.

The chassis 12 may include any structural member that supports movement of machine 10 and work implement 14. The chassis 12 may embody, for example, a stationary base frame connecting the power source 18 to the work implement 14, a moveable frame member of a linkage system, or any other structural member known in the art.

Numerous different work implements 14 may be attachable to a single machine 10 and be controllable via an operator (not shown). The work implement 14 may include any device used to perform a particular task such as, for example, a bucket, a fork arrangement, a blade, a shovel, a ripper, a broom, a snow blower, a propelling device, a cutting device, a grasping device, or any other task-performing device known in the art. The work implement 14 may be connected to the chassis 12 of the machine 10 via a direct pivot, via a linkage system, or in any other appropriate manner. The work implement 14 may be configured to pivot, rotate, slide, swing, lift, or move relative to machine 10 in any manner known in the art.

The operator cabin 16 may be configured to receive input from the operator indicative of a desired work implement movement. Specifically, the operator cabin 16 may include an interface device 22. The interface device 22 may embody, for example, a single- or multi-axis joystick located within the operator cabin 16. The interface device 22 may be a proportional-type controller configured to generate signals indicative of desired positions and/or orientations of the work implement 14. It is contemplated that additional and/or different interface devices may be included within the operator interface 16 such as, for example, wheels, knobs, push-pull devices, switches, buttons, pedals, and other interface devices known in the art.

Turning to the power source 18, it may be an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine such as a natural gas engine, or any other type of engine known in the art. It is contemplated that power source 18 may alternatively embody another source of power such as a fuel cell, a power storage device, an electric or hydraulic motor, or another source of power known in the art.

The traction device 19 may be, for example, a wheel, a belt, a track or any other traction device known in the art. Traction device 19 may be driven by the power source 18 to rotate and propel the machine 10 in accordance with an output rotation of the power source 18.

With the foregoing as general background for the machine 10, attention is directed to FIG. 2, wherein a hydraulic system 24 of the machine 10 is shown to include a plurality of fluid components that cooperate together to move work implement 14. Specifically, the hydraulic system 24 may include a tank 26 holding a supply of fluid, and a source 28 driven by power source 18 to draw and pressurize the fluid from the tank 26, and to direct the pressurized fluid to the hydraulic actuator 20. The hydraulic system 24 may also include a valve arrangement 30 disposed between the hydraulic actuator 20 and the tank 26 and the source 28 to regulate flows of fluid to and from the hydraulic actuator 20 that affect movement of the work implement 14.

The tank 26 may constitute a reservoir configured to hold a supply of fluid. The fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, or any other fluid known in the art. One or more hydraulic systems within machine 10 may draw fluid from and return fluid to the tank 26. It is also contemplated that hydraulic system 24 may be connected to multiple separate fluid tanks, if desired.

The source 28 may be configured to produce a flow of pressurized fluid and may be a pump such as, for example, a variable displacement pump, a fixed displacement variable delivery pump, a fixed displacement fixed delivery pump, or any other suitable source of pressurized fluid. The source 28 may be drivably connected to the power source 18 of the machine 10 by, for example, a countershaft, a belt (not shown), an electrical circuit (not shown), or in any other appropriate manner. It is contemplated that multiple sources of pressurized fluid may alternatively be interconnected to supply pressurized fluid to the hydraulic system 24, if desired.

The hydraulic actuator 20 may embody a fluid cylinder that connects the work implement 14 to the chassis 12 via a direct pivot, via a linkage system with the hydraulic actuator 20 acting as a member of the linkage system (shown in FIG. 1), or in any other appropriate manner. It is contemplated that a hydraulic actuator other than a fluid cylinder may alternatively be implemented within the hydraulic system 24 such as, for example, a hydraulic motor or another appropriate hydraulic actuator.

As illustrated in FIG. 2, the hydraulic actuator 20 may include a cylinder 32 and a piston assembly 34 disposed within the cylinder 32. One of the cylinder 32 and piston assembly 34 may be pivotally connected to the chassis 12, while the other of the cylinder 32 and piston assembly 34 may be pivotally connected to the work implement 14. It is contemplated that the cylinder 32 and/or piston assembly 34 may alternatively be fixedly connected to either the chassis 12 or the work implement 14, if desired. The cylinder 32 may be divided into a rod chamber 36 and a head chamber 38 by piston assembly 34. The rod and head chambers 36, 38 may be selectively supplied with pressurized fluid from the source 28 and selectively connected with the tank 26 to cause the piston assembly 34 to displace within the tube 32, thereby changing an effective length of the hydraulic actuator 20. The expansion and retraction of the hydraulic actuator 20 may function to assist in moving the work implement 14.

The piston assembly 34 may include a first hydraulic surface 40 and a second hydraulic surface 42 opposite the first hydraulic surface 40. An imbalance of force caused by fluid pressure acting on the first and second hydraulic surfaces 40, 42 may result in movement of the piston assembly 34 within the cylinder 32. For example, a force resulting from fluid pressure acting on the first hydraulic surface 40 being greater than a force resulting from fluid pressure acting on the second hydraulic surface 42 may cause the piston assembly 34 to retract within the cylinder 32 to decrease the effective length of the hydraulic actuator 20. Similarly, when a force caused by fluid pressure acting on the second hydraulic surface 42 is greater than a force caused by fluid pressure acting on the first hydraulic surface 40, the piston assembly 34 may displace and increase the effective length of the hydraulic actuator 20. A flow rate of fluid into and out of the rod and head chambers 36, 38 may affect a velocity of the hydraulic actuator 20, while a pressure of the fluid in contact with the first and second hydraulic surfaces 40, 42 may affect an actuation force of the hydraulic actuator 20. A sealing member (not shown), such as an o-ring, may be connected to the piston assembly 34 to restrict a flow of fluid between an internal wall of the cylinder 32 and an outer cylindrical surface 45 of piston assembly 34.

The valve arrangement 30 may include one or more valves configured to perform supply and drain functions associated with the head and rod chambers 36, 38 of the hydraulic actuator 20. In the embodiment of FIG. 2, the valve arrangement 30 includes a rod-end supply valve 44, a rod-end drain valve 46, a head-end supply valve 48, and a head-end drain valve 50. However, it is contemplated that a different configuration including a greater or lesser number of valves may alternatively be utilized to perform the functions of the valve arrangement 30, if desired. For example, in a second embodiment (not shown), the valve arrangement 30 could alternatively comprise only two valves, including a single head-end valve and a single rod-end valve that perform both supply and drain functions. In a third embodiment (not shown), the valve arrangement 30 could alternatively include a single valve capable of performing supply and drain functions for both the rod and head chambers 36, 38 of the hydraulic actuator 20. Although other valve arrangement embodiments may be possible, only the first embodiment of the valve arrangement 30 shown in FIG. 2 will be described in detail.

The rod-end supply valve 44 may be disposed between the source 28 and the rod chamber 36 and configured to regulate a flow of pressurized fluid directed to the rod chamber 36 in response to a commanded velocity. In one example, the rod-end supply valve 44 may be an independent metering valve (IMV) having a proportional spring-biased valve element (not shown) that is solenoid actuated and configured to move between a first position, at which fluid flow is blocked from the rod chamber 36, and a second position, at which fluid is allowed to flow into the rod chamber 36. The valve element of the rod-end supply valve 44 may be movable to any position between the first and second positions to vary the rate of flow into the rod chamber 36, thereby affecting the velocity of the hydraulic actuator 20.

Alternatively, the rod-end drain valve 46 may be disposed between the rod chamber 36 and the tank 26 and configured to regulate a flow of fluid from the rod chamber 36 to tank 26 in response to the commanded velocity. In one example, the rod-end drain valve 46 may be an IMV having a proportional spring-biased valve element that is solenoid actuated and configured to move between a first position, at which fluid is blocked from flowing from the rod chamber 36, and a second position, at which fluid is allowed to flow from the rod chamber 36. The valve element of the rod-end drain valve 46 may be movable to any position between the first and second positions to vary the rate of flow from the rod chamber 36, thereby affecting the velocity of the hydraulic actuator 20.

With respect to the head-end supply valve 48 it may be disposed between the source 28 and the head chamber 38 and configured to regulate a flow of pressurized fluid to the head chamber 38 in response to the commanded velocity. Specifically, the head-end supply valve 48 may be an IMV having a proportional spring-biased valve element configured to move between a first position, at which fluid is blocked from the head chamber 38, and a second position, at which fluid is allowed to flow into the head chamber 38. The valve element of the head-end supply valve 48 may be movable to any position between the first and second positions to vary the rate of flow into the head chamber 38, thereby affecting the velocity of the hydraulic actuator 20.

The head-end drain valve 50 may be disposed between the head chamber 38 and the tank 26 and configured to regulate a flow of fluid from the head chamber 38 to the tank 26 in response to the commanded velocity. Specifically, the head-end drain valve 50 may be an IMV having a proportional spring-biased valve element configured to move between a first position, at which fluid is blocked from flowing from the head chamber 38, and a second position, at which fluid is allowed to flow from the head chamber 38. The valve element of the head-end drain valve 50 may be movable to any position between the first and second positions to vary the rate of flow from the head chamber 38, thereby affecting the velocity of the hydraulic actuator 20.

Turning now to a focus of the present application, the hydraulic system 24 may also include a ride control system 52 configured to dampen unintended movements of the work implement 14 (i.e., movements not requested by the operator of the machine 10 via the interface device 22) during travel of the machine 10. The ride control system 52 may include an accumulator 54 and an accumulator valve 56. The accumulator valve 56 may be operable to selectively allow pressurized fluid into and/or out of the accumulator valve 56.

The accumulator 54 may be selectively communicated with the head chamber 38 by way of the accumulator valve 56 to selectively receive pressurized fluid from and direct pressurized fluid to the hydraulic actuator 20. In particular, the accumulator 54 may be a pressure vessel or other storage device filled with a compressible gas and configured to store pressurized fluid for future use as a source of fluid power. The compressible gas may include, for example, nitrogen or another appropriate compressible gas. As fluid within the head chamber 38 exceeds a predetermined pressure while the accumulator valve 56 and the head-end supply valve 48 are in a flow passing positions, fluid from the head chamber 38 and/or the source 28 may flow into the accumulator 54. Because the gas is compressible, it may act like a spring and compress as the fluid flows into the accumulator 54. When the pressure of the fluid within the head chamber 38 then drops below a predetermined pressure while the accumulator valve 56 and the head-end supply valve 48 are in the flow passing positions, the compressed gas within the accumulator 54 may urge the fluid from within the accumulator 54 back into the head chamber 38.

To help smooth out pressure oscillations within the hydraulic actuator 20, the hydraulic system 24 may absorb some energy from the fluid as the fluid flows between the head chamber 38 and the accumulator 54. The damping mechanism that accomplishes this may include a restrictive orifice disposed within either the accumulator valve 56, or within a fluid passageway between the accumulator 54 and the head chamber 38. Each time the work implement 14 moves in response to travel across uneven terrain, fluid may be squeezed through the restrictive orifice, and the energy expended to force the oil through the restrictive orifice may be converted into heat, which may then be dissipated from the hydraulic system 24. This dissipation of energy from the fluid may essentially absorb the bouncing energy, making for a smoother ride of the machine 10.

The accumulator valve 56, in one example, may be disposed in parallel with the head-end supply valve 48, and between the accumulator 54 and the head chamber 38. The accumulator valve 56 may be configured to regulate the flows of pressurized fluid between the accumulator 54 and the head chamber 38 in response to a ride control command. Specifically, the accumulator valve 56 may be an IMV having a proportional spring-biased valve element configured to move between a first position, at which fluid is blocked from flowing between the head chamber 38 and the accumulator 54, and a second position, at which fluid is allowed to flow between the head chamber 38 and the accumulator 54. When in a ride control mode of operation (i.e., when the ride control command has been issued), it is contemplated that instead of a fixed restrictive orifice, the valve element of the accumulator valve 56 may instead be controllably moved to any position between the flow passing and the flow blocking positions to vary the restriction and associated rate of fluid flow between the head chamber 38 and the accumulator 54, thereby affecting the cushioning of the hydraulic actuator 20 during travel of the machine 10.

The rod- and head-end supply and drain valves 44-50 and the accumulator valve 56 may be fluidly interconnected. In particular, the rod- and head-end supply valves 44, 48 may be connected in parallel to a common supply passageway 58 extending from the source 28. The rod- and head-end drain valves 46, 50 may be connected in parallel to a common drain passageway 60 leading to the tank 26. The rod-end supply and drain valves 44, 46 may be connected to a common rod chamber passageway 62 for selectively supplying and draining the rod chamber 36 in response to velocity commands. Similarly, the head-end supply and drain valves 48, 50 may be connected to a common head chamber passageway 64 for selectively supplying and draining the head chamber 38 in response to the velocity commands.

To control operations of the ride control system 52, as shown in FIG. 3, the hydraulic system 24 may further include a controller 66 in communication with the other components of the hydraulic system 24. The controller 66 may be a single microprocessor or multiple microprocessors that include a means for controlling an operation of the hydraulic system 24. Numerous commercially available microprocessors can be configured to perform the functions of the controller 66. It should be appreciated that the controller 66 could readily embody a general machine microprocessor capable of controlling numerous machine functions. In addition, the controller 66 may include a memory 67, a secondary storage device 68, a processor 69, and any other components for running an application. Various other circuits may be associated with the controller 66 such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry.

One or more maps 70 relating interface device position and command velocity information for the valve arrangement 30 and/or ride control system 52 may be stored in the memory of the controller 66. Each of these maps 70 may be in the form of a table, a map, an equation, or in another suitable form. The relationship maps may be automatically or manually selected and/or modified by the controller 66 to affect actuation of the hydraulic actuator 20.

The controller 66 may be configured to receive input from the interface device 22 and command an output signal 78 such as a velocity for the hydraulic actuator 20 in response to the input. Specifically, the controller 66 may be in communication with the rod- and head-end supply and drain valves 44-50 of the hydraulic actuator 20 and with the interface device 22. The controller 66 may receive the interface device position signal from the interface device 22, and reference the selected and/or modified relationship maps stored in the memory of the controller 66 to determine command velocity values. These velocity values may then be commanded of the hydraulic actuator 20 causing rod- and head-end supply and drain valves 44-50 to selectively fill or drain the rod and head chambers 36, 38 associated with the hydraulic actuator 20 to produce the desired movement of the work implement 14.

With specific regard to ride controls, the controller 66 may also be configured to initiate the ride control mode of operation. In particular, the controller 66 may either be manually switched to the ride control mode of operation as explained in further detail below or may automatically enter the ride control mode of operation in response to one or more inputs as also described below. A switch 71 accessible by the operator may be provided to facilitate this process, whereby the user can select one of a number of options, such as, but not limited to, automatic 71 a, off 71 b and manual 71 c. When in the ride control mode of operation, the controller 66 may cause the valve elements of the rod-end supply valve 44 and head-end drain valve 50 to move to or remain in the flow blocking positions. The controller 66 may simultaneously or subsequently move the valve elements of rod-end drain valve 46, head-end supply valve 48, and the accumulator valve 56 to the flow passing positions. As described above, the accumulator valve 56 may be moved to the flow passing position to allow fluid flow between the accumulator valve 56 and the head chamber 38. The rod-end drain valve 46 may be moved to the flow passing position to prevent hydraulic lock during an up-bounce of the work implement 14 as fluid is flowing from the accumulator 54 into the head chamber 38. It is also contemplated that the valve elements of the rod-end drain valve 46 and head-end supply valve 48 may be selectively positioned between the flow passing and flow blocking positions to vary the restriction of the fluid exiting and/or entering the rod and head chambers 36, 38, thereby adjusting dampening during the ride control mode of operation. To minimize undesired movement of the work implement 14 upon initiation of the ride control mode of operation, the pressure of the fluid within the accumulator 54 may be substantially matched to the pressure within the head chamber 38 in a conventional manner, before fluid communication between the accumulator 54 and head chamber 38, if desired.

One or more sensors 72 and a timer 73 may be associated with controller 66 to facilitate precise control of ride control system 52. A sensor 72 a may be located to monitor a speed of the machine 10, for example a rotational speed of the traction device 19 or a travel speed of the machine 10. The sensor 72 a may generate a signal indicative of the speed measurement and send this signal to the controller 66. Alternatively, or in addition to, the sensor 72 a, a sensor 72 b may be employed to sense that a parking brake 74 of the machine 10 is engaged. In other embodiments, other parameters may be used to detect that the machine 10 is stationary. For example, a sensor 72 c may be employed to sense that a transmission 76 of the machine 10 is in a certain gear, such as neutral, a sensor 72 d may be used to detect that the implement 14 is on the ground, or any one of a number of other parameters could be used to sense that the machine is stationary.

The timer 73 may be a digital or analog type device configured to track a time elapsed since the machine 10 begins operation, a time elapsed since a travel speed of the machine 10 exceeds a setpoint, a time elapsed since the machine 10 enters a ride control mode of operation, or any other similar time measurement. The timer 73 may generate a signal indicative of the time measurement and send this signal to the controller 66.

Referring now to FIG. 4, a flowchart depicting a sample sequence of steps which may be employed by the machine 10 are depicted. It is to be understood that this flowchart is merely exemplary and other variations and logic, including additional steps, may be employed. However, the logic of the present disclosure has as a desired result the engagement of the ride control in a manual mode only when the parking brake of the machine is engaged or some other parameter is sensed to indicate that the machine is stationary. In so doing, damage to valving of the ride control system 52 is avoided.

Starting with a first step 80, the ride control system 52 determines if the switch 71 is in the automatic position. If in fact the switch 71 is in the automatic position as indicated by step 82, the controller 66 then determines if the speed of the machine 10 is above the predetermined threshold as indicated in step 84. If the controller determines that the speed of the machine 10 is above the predetermined threshold as indicated by step 86, the controller 66 allows the ride control arrangement 52 to be engaged as indicated in step 88. However, if the controller 66 determines that the speed of the machine 10 is below the predetermined threshold as indicated by step 90, the controller does not allow the ride control arrangement 52 to be engaged as indicated in step 92.

Turning back to the top decision square of FIG. 4, if the controller determines that the switch 71 is not in the automatic position as indicated by step 94, the controller then determines if the ride control switch 71 is in the manual position as indicated by step 96. If the controller 66 determines that the ride control switch 71 is in the manual position as indicated by step 98, the controller 66 then determines in step 100 if the parking brake 74 is engaged. Again, however, any number of other parameters can be sensed to determine whether the machine 10 is stationary, including but not limited to whether the speed of the machine is sensed at zero, whether the machine transmission is in neutral or some other disengaged gear, or if the operator controls and/or implement levers indicate that the work implement is on the ground.

Returning to the flowchart of FIG. 4, if it is determined that the parking brake 74 is engaged as indicated by step 102, then the controller 66 causes the ride control system 52 to become engaged as indicated in step 104. However, if the controller 66 determines that the parking brake 74 is not engaged as indicated by step 106, the controller 66 does not allow the ride control system 52 to become engaged as indicated in step 108.

Finally, returning back to step 96, if the controller 66 determines that the switch 71 is not in the manual mode, and is already been determined not to be in the automatic position, the controller 66 determines in step 110 that the ride control switch 71 is in the off position as shown in step 112. In this event, the ride control system 52 is not engaged as shown by step 114.

INDUSTRIAL APPLICABILITY

The disclosed hydraulic system may be applicable to any mobile machine that includes a hydraulic actuator connected to a work implement. The disclosed hydraulic system may improve a ride control mode of operation by minimizing undesired activations that can attribute to accelerated wear of the hydraulic system and discomfort or frustration for the operator. Moreover, the ride control system ensures that it cannot be employed when the system is in a manual mode unless the parking brake is on or some other parameter is sensed to ensure the machine is not moving. In doing so, damage to the valving of the ride control system is avoided.

Because the disclosed ride control mode of operation may be selectively and automatically activated based on both a travel speed and an elapsed amount of time since the travel speed exceeds the setpoint, the frequency of activation and deactivation events may be reduced, while still providing adequate cushioning of work implement 14. And, a reduction in the activation/deactivation of the ride control mode of operation may help extend the component life of hydraulic system 24.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed hydraulic system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed hydraulic system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

What is claimed is:
 1. A hydraulic ride control system for a mobile machine having an implement, the system comprising: a hydraulic actuator extending from the machine and connected to an implement; an accumulator; a valve controlling fluid flow between the hydraulic actuator and the accumulator; a sensor; a ride control selection switch; and a controller receiving signals from the sensor and the ride control selection switch and, when the ride control switch is in manual position, only allowing fluid flow between the hydraulic activator and the accumulator when the sensor indicates a predetermined value.
 2. The hydraulic ride control system of claim 1, wherein the sensor is a parking brake position sensor and the predetermined value indicates that the parking brake is engaged.
 3. The hydraulic ride control system of claim 1, wherein the sensor is a mobile machine speed sensor and the predetermined value indicates the mobile machine is not moving.
 4. The hydraulic ride control system of claim 1, wherein the sensor is a mobile machine gear sensor and the predetermined value indicates the mobile machine is in neutral.
 5. The hydraulic ride control system of claim 1, wherein the sensor is an implement lever position sensor and the predetermined value indicates the implement is on the ground.
 6. The hydraulic ride control system of claim 1, wherein the ride control selection switch is adapted to be in one of an auto, off, and manual position.
 7. A method of controlling ride of a mobile machine having an implement, the method comprising: detecting the position of a ride control switch; sensing a parameter indicative of movement of the mobile machine; and when the ride control switch is detected to be in a manual mode, allowing activation of ride control only when the sensed parameter indicates the mobile machine is not moving.
 8. The method of claim 7, wherein the ride control switch has auto, off and manual positions, and the detecting determines if the ride control switch is in the manual mode.
 9. The method of claim 7, wherein the mobile machine includes a parking brake and the sensing a parameter involves sensing a position of a parking brake to ensure the parking brake is engaged.
 10. The method of claim 7, wherein the mobile machine includes a machine speed sensor and the sensing a parameter involves sensing a speed of the mobile machine to ensure the mobile machine is stationary.
 11. The method of claim 7, wherein the mobile machine includes a gear sensor and the sensing a parameter involves sensing the gear a transmission of the mobile machine is in to ensure the mobile machine is in neutral.
 12. The method of claim 7, wherein the mobile machine includes an implement lever position sensor, and the sensing a parameter involves sensing the position of the implement lever to ensure the implement is on the ground.
 13. A mobile machine, comprising: a chassis; an engine supported on the chassis; a traction device supporting the chassis; an implement movably connected to the chassis; a hydraulic actuator connected between the implement and the chassis; a ride control system; a ride control selection switch; a sensor sensing a parameter indicative of movement of the mobile machine; and a controller engaging the ride control system when the ride control selection switch is in a manual mode only if a sensed parameter from the sensor reaches a predetermined value.
 14. The mobile machine of claim 13, wherein the mobile machine further includes a parking brake and the sensor senses whether the parking brake is engaged.
 15. The mobile machine of claim 13, wherein the mobile machine further includes a speed sensor and the sensor senses whether the mobile machine is stationary.
 16. The mobile machine of claim 13, wherein the mobile machine further includes a gear sensor and the sensor senses whether the gear is in neutral.
 17. The mobile machine of claim 13, wherein the mobile machine further includes an implement lever position sensor and the sensor senses whether the implement is on the ground.
 18. The mobile machine of claim 13, wherein the ride control selection switch has auto, off, and manual positions.
 19. The mobile machine of claim 18, wherein the ride control system includes an accumulator and a valve between the accumulator and the hydraulic actuator.
 20. The mobile machine of claim 19, wherein the controller only allows fluid communicator between the accumulator and the hydraulic actuator through the valve when the ride control selection switch is in the manual position, and when the sensor senses that the mobile machine is stationary. 